Business process engineering, TQM$,$ and Six Sigma programs and processes differ primarily because

a$)$ business process engineering and TQM aim at one$-$time quantum improvement, whereas continuous improvement programs like Six Sigma aim at ongoing improvements.

b$)$ business process reengineering has to be used exclusively, whereas continuous improvement tools like TQM and Six Sigma can be used in tandem$.$

c$)$ business process reengineering aims at improved productivity and reduced costs, whereas TQM and Six Sigma focus on better product quality and greater customer satisfaction.